Subway

I received a sheet of Subway coupons in the mail and have used several of them on the sheet at this Subway location. Yesterday I ordered two footlong sandwhiches and presented the "Free Footlong when you buy ANY Footlong" coupon. The person who made the sandwich told the cashier that they didn't take the "Buy one get one free" coupon. I told him that I had used some of the other coupons from the same sheet that didn't expire until 6/11/21. He said that when he tried to scan the coupon the day before it wouldn't take it. The cashier tried to scan it and it wouldn't scan. She gave it back to me. I would not have ordered two sandwiches, except for having the coupon. How can a franchise pick and choose which coupons they are going to accept? I go to this store often but will not be going back again ever. I expect to have one of these sandwiches refunded.